Apparatus and Method for Tensioning a Gun Barrel Liner

ABSTRACT

Tensioned gun barrel liners, and methods and apparatus for tensioning gun barrel liners are disclosed. Tensioned gun barrels have been shown to have superior performance. The apparatus allows for axial strain to be imparted into the gun barrel using mechanical means while other embodiments utilize thermal expansion of the material such as metal that is used for the gun barrel liner to introduce the strain and maintain it using other mechanical means or applied material such as composites.

TECHNICAL FIELD

The present disclosure relates generally to firearm components, and more specifically to an apparatus and a method for tensioning a gun barrel liner.

BACKGROUND

Many different types of firearms are known. Firearms inflict damage on targets by launching projectiles driven by a propellant towards the target. The purpose is to accelerate a projectile to very high speeds so that it can hit a target at a distance with sufficient force to make a desired impact.

The mechanism that generates force to expel the projectile is typically a controlled explosion that is initiated when the trigger is pulled. A spring-loaded metal piece is arranged to strike a volatile substance that ignites when struck called a primer. The primer causes a spark inside the casing where gunpowder is held, creating a controlled explosion. The controlled expansion of burning propellant or gunpowder generates force or pressure, applied to the base of the projectile such as a bullet, which in turn is equivalent to inner diameter of the barrel. A projectile traveling through a barrel is characterized by increasing acceleration as the expanding gases push on it.

Barrels greatly affect the acceleration and other kinetic characteristics of the projectile. A barrel is thus a very important element of a firearm.

It has been shown that tensioned barrels have been proven to be more accurate than conventional untensioned barrels, many firearms still utilize untensioned barrels or components.

It is thus desirable to have improved methods and apparatus to impart the required tension into a gun barrel.

SUMMARY OF INVENTION

In accordance with one aspect of the present invention, there is provided a method of tensioning barrel liner comprising: stretching the barrel liner along a longitudinal axial direction from at least one of a distal end and a proximal end of the barrel liner, such that the barrel liner is under axial strain in a tensioned state; and restraining the barrel liner in its tensioned state such that the barrel liner remains under said axial strain.

In accordance with one aspect of the present invention, there is provided an apparatus for tensioning a barrel liner. The apparatus includes a implement which may be a threaded rod for insertion along the central axis of the barrel liner; and securing elements securing the implement to the liner. The implement is operable to engage the barrel liner to cause axial strain in the barrel liner along a central axis of the barrel liner, the securing elements are operable to secure the barrel liner to the implement, to prevent displacement a portion of the implement relative to the barrel liner, such that movement of the said portion of the implement causes said axial strain. The securing elements may be in the form of a stop for placement at a proximal end of the barrel liner to stop the implement or rod which may be disposed within the barrel liner; and a cap for capping a distal end of the barrel liner, the cap having an opening for allowing the rod therethrough, wherein as the rod is introduced to the distal end of the barrel liner and progresses longitudinally along the central axis, the stop and the cap preventing further longitudinal displacement of the rod relative to the barrel liner, and instead causing axial strain in the barrel liner, such that the barrel liner remains under axial strain.

In accordance with another aspect of the present invention, there is provided a gun barrel produced by a process comprising: providing barrel liner and a structural external feature; placing the barrel liner under axial strain; and applying the external feature while the barrel liner is under said axial strain.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings, which illustrate one or more embodiments:

FIG. 1 is a side elevational view of a conventional untensioned gun barrel liner;

FIG. 2 is a longitudinal sectional view of the barrel liner of FIG. 1, disposed in a barrel tensioning apparatus; and

FIG. 3 is a side elevational view of a tensioned gun barrel liner exemplary of an embodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT

Tensioned gun barrel liners, and methods and apparatus for tensioning gun barrel liners are disclosed. Tensioned gun barrels have been shown to have superior performance including increased rigidity, reduced vibration and increased accuracy. Some of the exemplary apparatuses and methods provided in this disclosure allow for axial strain to be imparted into the gun barrel using mechanical means. Other embodiments utilize thermal expansion of the material used for the gun barrel liner to introduce the strain and maintain it using other mechanical means.

Directional terms such as “top,” “bottom,” “upwards,” “downwards,” “left,” “right,” “vertically,” and “laterally” are used in the following description for the purpose of providing relative reference only, and are not intended to suggest any limitations on how any article is to be positioned during use, or to be mounted in an assembly or relative to an environment. The use of the word “a” or “an” when used herein in conjunction with the term “comprising” may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one” and “one or more than one.” Any element expressed in the singular form also encompasses its plural form. Any element expressed in the plural form also encompasses its singular form. The term “plurality” as used herein means more than one; for example, the term “plurality includes two or more, three or more, four or more, or the like.

In this disclosure, the terms “comprising”, “having”, “including”, and “containing”, and grammatical variations thereof, are inclusive or open-ended and do not exclude additional, un-recited elements and/or method steps. The term “consisting essentially of” when used herein in connection with a composition, use or method, denotes that additional elements, method steps or both additional elements and method steps may be present, but that these additions do not materially affect the manner in which the recited composition, method, or use functions. The term “consisting of” when used herein in connection with a composition, use, or method, excludes the presence of additional elements and/or method steps.

In this disclosure, the term “firearm” refers to a rifle, a pistol, or any other portable gun, which utilizes a propellant to propel a projectile towards a target.

In this disclosure, the terms “barrel”, “firearm barrel” and “gun barrel” refer to a straight tube, which forms part of a firearm, and through which a contained rapid expansion of high-pressure gas is introduced behind a projectile in order to propel it out of the front end of the barrel at a high velocity.

In this disclosure, the terms “barrel liner”, “gun barrel liner”, and “firearm barrel liner” refer to the inner component of a firearm barrel. The barrel liner may include the fluted section of a barrel.

FIG. 1 depicts an schematic diagram of a barrel liner 100. Barrel liner 100 has an elongate cylindrical body 104 defined by a central longitudinal axis 108 with a neck 102 near the proximal end.

Barrel liner 100 is typically made of metal or another appropriate material. Materials such as steel, carbon steel, other steel alloys, ceramic and composite materials can also be used in alternative embodiments. As may be appreciated, although the depicted embodiment in FIG. 1 has a cylindrical body 104 having a circular cross-section, in other embodiments, the cross-section of the barrel body may have an elliptical, polygonal or other shapes.

The barrel liner 100 provides a wear surface for a projectile. To tension the barrel liner 100 of FIG. 1 to a desired axial strain, in accordance with an embodiment of the present invention, a tensioning apparatus such as that shown in FIG. 2 is used.

Mechanical Embodiment

As shown in FIG. 2, an exemplary tensioning apparatus 200 includes an implement such as a threaded rod 202 disposed along, in parallel or through central axis 108 of barrel liner 100. Securing elements such as a stop 204 and a cap 206 are used to secure the barrel liner 100 to the apparatus 200. Components of barrel liner 100 are the same as those shown in FIG. 1 and will not be further described.

In operation, using apparatus 200, axial strain is applied using the threaded rod 202. Stop 204 and cap 206 secure the barrel liner 100 in place while the threaded rod 202 progresses longitudinally relative to the barrel liner 100 along the direction of central axis 108. The securing elements in the form of stop 204 and cap 206 are used to prevent relative displacement of the implement in the form of rod 202 so that further movement of the threaded rod 202 causes tension or axial strain instead.

Once the barrel liner 100 is tensioned, a restraining element is introduced to keep the barrel liner 100 tensioned or under axial strain. The restraining element may be an external structural material applied to the barrel liner 100.

In one embodiment, the restraining element is a composite material, such as carbon composite material that is applied to the tensioned barrel liner 100. In other embodiments using advanced composite resin applied to the tensioned barrel liner 100. The advanced composite resin may be cured to a hardened state through heat, to keep the liner 100 restrained or tensioned.

Once the composite is cured the threaded rod 202 is removed from the barrel line 100, the cured composite prevents the barrel liner 100 from returning to its natural state resulting in a residual axial strain. Due to Poisson's ratio v which measures the expansion or contraction of a material in directions perpendicular to the direction of loading, there may be a resultant hoop strain as well.

The barrel liner 100 may have stops or features to provide a mechanical lock other than just bonding that would occur between a composite (not illustrated) and barrel liner 100.

Thermal Embodiment

The axial strain may be produced using thermal means. In an alternate embodiment, barrel liner 100 may be heated or otherwise subjected to a higher temperate so as to cause its expansion. Thereafter, the expanded barrel liner is restrained using an external feature such as a composite applied to the heated barrel liner. The combination of the heated liner and the applied material or external feature is then cooled. As the barrel liner tends to contract further under cooling than the applied material, the cooling step causes axial strain in the barrel liner 100.

As would be appreciated, the coefficient of thermal expansion of the barrel liner (CTE_(b)) is typically higher than for the applied material (CTE_(a)) causing axial strain in the barrel liner 100 upon cooling.

FIG. 3 depicts a schematic diagram of a barrel liner 100 a under axial strain. Barrel liner 100 a is essentially the same as barrel liner 100 of FIG. 1 except for the presence of axial strain leading to slightly larger dimensions. Like parts in FIG. 3 and FIG. 1 are labeled with like reference numerals, with a prime symbol (′) or a letter suffix (e.g., ‘a’) used to distinguish the elements of FIG. 3 from their counterparts in FIG. 1. Barrel liner 100 a therefore also has an elongate cylindrical body 104 a defined by a central longitudinal axis 108 with a neck 102 a at near the proximal end.

Alternate Embodiments

Alternate embodiments of the present invention include a method of tensioning barrel liner comprising: stretching the barrel liner along a longitudinal axial direction from at least one of a distal end and a proximal end of the barrel liner, such that the barrel liner is under axial strain; and securing the barrel liner in its expanded state such that the barrel liner remains under said axial strain.

In another embodiment of the above method, securing the barrel liner includes restraining the barrel liner in place while under said axial strain using restraining elements, features or composites.

In some embodiments, thermal expansion is exploited to stretch or expand the elongate barrel liner. This may involve heating the barrel liner so as to cause expansion; restraining the heated barrel liner using a restraining element; and cooling the heated barrel liner; wherein upon said cooling, the barrel liner is restrained by the external feature from contracting, thereby resulting in axial strain. The restraining or cooling may include applying external material to the heated barrel liner.

In another embodiment of the present invention, an apparatus for tensioning a barrel liner having a central axis is provided. The apparatus comprises: a implement such as a rod which may be threaded, for insertion or disposition along the central axis of the barrel liner; and securing elements in the form of a stop and a cap. The stop is for placement at a proximal end of the barrel liner to stop the rod disposed within the barrel liner; and the cap is for capping a distal end of the barrel liner. Where the implement is a rod, the cap may have an opening for allowing the rod therethrough, wherein as the rod is introduced to the distal end of the barrel liner and progresses longitudinally along the central axis, the stop and the cap prevent further longitudinal displacement of the rod relative to the barrel liner and instead cause axial strain in the barrel liner. Thereafter, other means of tensioning such as applying materials may be used so that barrel liner remains under axial strain even after the securing elements are disengaged from the barrel liner or the implement. The implement may be a threaded rod.

In other embodiments of the apparatus, different elements or fixtures other than stop 204 and cap 206 may be used to secure a barrel liner in place. Implements other than threaded rod 202 may be used to cause axial strain in the liner, along the direction of central axis 108. The implement need not necessarily be inserted in the liner in all embodiments and operations, but need only cause axial strain.

In another embodiment of the present invention, a process for tensioning a gun barrel or liner is provided. The process comprises: providing barrel liner and a structural external feature; placing the barrel liner under axial strain; and applying the external feature while the barrel liner is under said axial strain.

In some embodiments, the barrel liner is made up of one or more of steel, carbon steel, steel alloy, ceramic and composite material. In other embodiments, the gun barrel liner is steel or stainless steel or ceramic. The external feature may be a composite material including one or more of carbon, glass, Kevlar™ and fibrous reinforcing material and the composite material comprises any one of epoxy or any matrix polymer.

In some embodiments of the gun barrel the external feature comprises a metal matrix. In others it comprises wire and the wire may be applied through a winding process.

The composite may be applied via filament winding or through roll wrapping or through braiding.

In some embodiments, the barrel liner could be tensioned by a torqued threaded rod positioned in the center of the barrel. The barrel liner may be made from an existing barrel that is machined to a smaller diameter.

The above-described embodiments are intended to be examples of the present disclosure and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention, which is defined solely by the claims appended hereto. 

What is claimed is:
 1. A method of tensioning a barrel liner, the method comprising: a) stretching the barrel liner along a longitudinal axial direction from at least one of a distal end and a proximal end of the barrel liner, to place the barrel liner under axial strain in a tensioned state; and b) restraining the barrel liner in the tensioned state such that the barrel liner remains under said axial strain.
 2. The method of claim 1, wherein said restraining comprises one or more restraining elements.
 3. The method of claim 1, wherein said restraining comprises applying external material.
 4. The method of claim 3, wherein said external material comprises one or more of: composite material, advanced composite material and carbon composite material.
 5. The method of claim 1, wherein said stretching is achieved by thermal expansion.
 6. The method of claim 5, comprising: a) heating the barrel liner to cause said stretching; b) applying a restraining element to the heated barrel liner in said tensioned state; c) cooling the heated barrel liner; wherein upon said cooling, the barrel liner remains in said tensioned state restrained by the restraining element from contracting, thereby resulting in said axial strain.
 7. The method of claim 6, wherein said cooling comprises applying external material to the heated barrel liner.
 8. The method of claim 6, wherein said restraining element comprises external material applied to the heated barrel liner and then subsequently cooled.
 9. An apparatus for tensioning a barrel liner, the apparatus comprising: an implement for engaging the barrel liner; and securing elements for securing the implement to the barrel liner, wherein the implement is operable to engage the barrel liner to cause axial strain in the barrel liner along a central axis of the barrel liner, the securing elements are operable to secure the barrel liner to the implement, to prevent displacement a portion of the implement relative to the barrel liner, such that movement of the said portion of the implement causes said axial strain.
 10. The apparatus of claim 9, wherein the implement is a rod; and the securing elements comprise: a stop for placement at a proximal end of the barrel liner to stop the rod disposed within the barrel liner; and a cap for capping a distal end of the barrel liner, the cap having an opening for allowing the rod therethrough, wherein as the rod is introduced through the distal end of the barrel liner and progresses longitudinally along the central axis, the stop and the cap prevent further longitudinal displacement of the rod relative to the barrel liner, and instead causes said axial strain in the barrel liner.
 11. The apparatus of claim 10, wherein the rod is a threaded rod and the opening is threaded.
 12. A gun barrel produced by a process comprising: a) providing barrel liner and a structural external feature; b) placing the barrel liner under axial strain; and c) applying the external feature while the barrel liner is under said axial strain.
 13. The gun barrel of claim 12, wherein the barrel liner comprises one or more of steel, carbon steel, steel alloy, ceramic and composite material.
 14. The gun barrel of claim 12, wherein the barrel liner is steel or stainless steel.
 15. The gun barrel of claim 12, wherein the barrel liner is ceramic.
 16. The gun barrel of claim 12, wherein the external feature is a composite material.
 17. The gun barrel of claim 16, wherein the composite material comprises one or more of carbon, glass, Kevlar™ and fibrous reinforcing material.
 18. The gun barrel of claim 16, wherein the composite material comprises any one of epoxy, or any matrix polymer.
 19. The gun barrel of claim 12, wherein the external feature comprises a metal matrix.
 20. The gun barrel of claim 12, wherein the external feature comprises wire.
 21. The gun barrel of claim 16, wherein the composite is applied via filament winding.
 22. The gun barrel of claim 16, wherein the composite is applied through roll wrapping.
 23. The gun barrel of claim 16, wherein the composite is applied through braiding.
 24. The gun barrel of claim 20, wherein the wire is applied through a winding process.
 25. The gun barrel of claim 12, wherein the barrel liner is tensioned by a torqued threaded rod positioned in the center of the barrel.
 26. The gun barrel of claim 12, tensioned by thermal expansion.
 27. The gun barrel of claim 12, made from an existing barrel that is machined to a smaller diameter. 